The present disclosure relates to nanoporous deposition, and specifically, to forming nanoporous contacts on a receiving substrate without a seed layer.
During microfabrication of electronic components, components are bonded together to create electrical connections between the components. In some situations, materials with different thermal expansion properties are bonded together. However, the different thermal expansion properties can be problematic when the high temperatures (e.g., 200-300° C.) and pressures are used during typical bonding processes.
In some situations, nanoporous materials are formed to facilitate bonding between electrical components. To form a nanoporous material, a co-alloy is deposited on a seed layer (e.g., through a plating process). Afterwards, the co-alloy is de-alloyed to form the nanoporous material. To prevent lateral shorts between adjacent electrical contacts, the seed layer is removed from the substrate. However, the difficulty of removing the seed layer can limit the form factors of the nanoporous material.
For example, if the spacing between electrical contacts is a few micrometers or less, wet etching processes to remove the seed layer can also remove the formed nanoporous material. As such, a dry etching process may be used. However, during a dry etching process the seed layer will be re-deposited within the etch chamber, making the etch chamber unusable for other purposes. Additionally during the dry etching process, materials of the seed layer may be re-deposited on the sidewalls of the small nanoporous metal features. Furthermore, typical dry etching processes, such as inductively coupled plasma etching (ICP) or reactive ion-etching (ME) are ineffective because the metal species in nanoporous materials may not form volatile species during the etching process. An ion milling process may be used. However, the ion milling process may involve a masking or shuttering process or a sacrificial etch mask to prevent the ion milling process from altering or damaging the nanoporous material or other components. Thus, seed layer removal process is difficult and costly, especially as the form factor of electrical components decreases.